Method and apparatus for developing a control architecture for coordinating shift execution and engine torque control

ABSTRACT

A method for controlling a powertrain system including a transmission mechanically coupled to an engine and an electric machine includes monitoring operator inputs to an accelerator pedal, determining a preferred operating point of the powertrain based upon the operator inputs, determining a preferred operating range state of the transmission based upon the preferred operating point, determining lead control signals for the engine and the transmission based upon the preferred operating point and the preferred operating range state of the transmission, determining immediate control signals for the electric machine and the transmission, controlling operation of the engine based upon the lead control signals for the engine and the transmission, and controlling operation of the electric machine based upon the immediate control signals for the electric machine and the transmission.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/985,635 filed on Nov. 5, 2007 which is hereby incorporated herein byreference.

TECHNICAL FIELD

This disclosure pertains to control systems for electro-mechanicaltransmissions.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Known powertrain architectures include torque-generative devices,including internal combustion engines and electric machines, whichtransmit torque through a transmission device to an output member. Oneexemplary powertrain includes a two-mode, compound-split,electro-mechanical transmission which utilizes an input member forreceiving motive torque from a prime mover power source, preferably aninternal combustion engine, and an output member. The output member canbe operatively connected to a driveline for a motor vehicle fortransmitting tractive torque thereto. Electric machines, operative asmotors or generators, generate an input torque to the transmission,independently of an input torque from the internal combustion engine.The electric machines may transform vehicle kinetic energy, transmittedthrough the vehicle driveline, to electrical energy that is storable inan electrical energy storage device. A control system monitors variousinputs from the vehicle and the operator and provides operationalcontrol of the powertrain, including controlling transmission operatingrange state and gear shifting, controlling the torque-generativedevices, and regulating the electrical power interchange among theelectrical energy storage device and the electric machines to manageoutputs of the transmission, including torque and rotational speed.

Transmissions within a hybrid powertrain, as described above, serve anumber of functions by transmitting and manipulating torque in order toprovide torque to an output member. In order to serve the particularfunction required, the transmission selects between a number ofoperating range states or configurations internal to the transmissiondefining the transfer of torque through the transmission. Knowntransmissions utilize operating range states including fixed gear statesor states with a defined gear ratio. For example, a transmission canutilize four sequentially arranged fixed gear states and allow selectionbetween the four gear states in order to provide output torque through awide range of output member speeds. Additively or alternatively, knowntransmissions also allow for continuously variable operating rangestates or mode states, enabled for instance through the use of aplanetary gear set, wherein the gear ratio provided by the transmissioncan be varied across a range in order to modulate the output speed andoutput torque provided by a particular set of inputs. Additionally,transmissions can operate in a neutral state, ceasing all torque frombeing transmitted through the transmission. Additionally, transmissionscan operate in a reverse mode, accepting input torque in a particularrotational direction used for normal forward operation and reversing thedirection of rotation of the output member. Through selection ofdifferent operating range states, transmissions can provide a range ofoutputs for a given input.

Operation of the above devices within a hybrid powertrain vehiclerequire management of numerous torque bearing shafts or devicesrepresenting connections to the above mentioned engine, electricalmachines, and driveline. Input torque from the engine and input torquefrom the electric machine or electric machines can be appliedindividually or cooperatively to provide output torque. However, changesin output torque required from the transmission, for instance, due to achange in operator pedal position or due to an operating range stateshift, must be handled smoothly. Particularly difficult to manage areinput torques, applied simultaneously to a transmission, with differentreaction times to a control input. Based upon a single control input,the various devices can change respective input torques at differenttimes, causing increased abrupt changes to the overall torque appliedthrough the transmission. Abrupt or uncoordinated changes to the variousinput torques applied to a transmission can cause a perceptible changein acceleration or jerk in the vehicle, which can adversely affectvehicle drivability.

Various control schemes and operational connections between the variousaforementioned components of the hybrid drive system are known, and thecontrol system must be able to engage to and disengage the variouscomponents from the transmission in order to perform the functions ofthe hybrid powertrain system. Engagement and disengagement are known tobe accomplished within the transmission by employing selectivelyoperable clutches. Clutches are devices well known in the art forengaging and disengaging shafts including the management of rotationalvelocity and torque differences between the shafts. Engagement orlocking, disengagement or unlocking, operation while engaged or lockedoperation, and operation while disengaged or unlocked operation are allclutch states that must be managed in order for the vehicle to operateproperly and smoothly.

Clutches are known in a variety of designs and control methods. Oneknown type of clutch is a mechanical clutch operating by separating orjoining two connective surfaces, for instance, clutch plates, operating,when joined, to apply frictional torque to each other. One controlmethod for operating such a mechanical clutch includes applying ahydraulic control system implementing fluidic pressures transmittedthrough hydraulic lines to exert or release clamping force between thetwo connective surfaces. Operated thusly, the clutch is not operated ina binary manner, but rather is capable of a range of engagement states,from fully disengaged, to synchronized but not engaged, to engaged butwith only minimal clamping force, to engaged with some maximum clampingforce. Clamping force applied to the clutch determines how much reactivetorque the clutch can carry before the clutch slips. Variable control ofclutches through modulation of clamping force allows for transitionbetween locked and unlocked states and further allows for managing slipin a locked transmission. In addition, the maximum clamping forcecapable of being applied by the hydraulic lines can also vary withvehicle operating states and can be modulated based upon controlstrategies.

Transition from one operating state range to another operating staterange involves transitioning at least one clutch state. An exemplarytransition from one fixed gear state to another involves unloading afirst clutch, transitioning through a freewheeling, wherein no clutchesremain engaged, or inertia speed phase state, wherein at least oneclutch remains engaged, and subsequently loading a second clutch. Adriveline connected to a locked and synchronized clutch, prior to beingunloaded, is acted upon by an output torque resulting through thetransmission as a result of input torques and reduction factors presentin the transmission. In such a torque transmitting state, thetransmission so configured during a shift is said to be in a torquephase. In a torque phase, vehicle speed and vehicle acceleration arefunctions of the output torque and other forces acting upon the vehicle.Unloading a clutch removes all input torque from a previously locked andsynchronized clutch. As a result, any propelling force previouslyapplied to the output torque through that clutch is quickly reduced tozero. In one exemplary configuration, another clutch remains engaged andtransmitting torque to the output while the transmission synchronizesthe second clutch. In such a configuration, the transmission is in aninertia speed phase. As the second clutch to be loaded is synchronizedand loaded, the transmission again enters a torque phase, whereinvehicle speed and vehicle acceleration are functions of the outputtorque and other forces acting upon the vehicle. While output torquechanges or interruptions due to clutch unloading and loading are anormal part of transmission operating range state shifts, orderlymanagement of the output torque changes reduces the impact of the shiftsto drivability.

Slip, or relative rotational movement between the connective surfaces ofthe clutch when the clutch connective surfaces are intended to besynchronized and locked, occurs whenever reactive torque applied to theclutch exceeds actual capacity torque created by applied clamping force.Slip in a transmission results in unintended loss of torque controlwithin the transmission, results in loss of engine speed control andelectric machine speed control caused by a sudden change in back-torquefrom the transmission, and results in sudden changes to vehicleacceleration, creating adverse affects to drivability. Therefore, clutchtransitions are known to include control measures to reduce or eliminatethe occurrence of clutch slip during torque phases including duringtransitional locking and unlocking states.

Input torques, as described above, can originate from a number of hybridpowertrain components simultaneously. Clutches, in order to avoid slip,remain synchronized and locked with a minimum clutch torque capacitywhenever reactive torque is transmitted through the clutch. Clutchtorque capacity is a function of hydraulic pressure applied to theclutch. Greater hydraulic pressure in the clutch results in a greaterclamping force within the clutch and a resulting higher clutch torquecapacity. Because output acceleration throughout powertrain operation isa function of output torque, the various input torques, acting throughthe transmission to create output torque, directly impact outputacceleration. Minimizing an impact upon output acceleration throughoutclutch operation, including transmission operating range state shifts,can therefore be benefited by an orderly coordination of input torquesresulting from various hybrid powertrain components.

SUMMARY

A method for controlling a powertrain system including a transmissionmechanically coupled to an engine and an electric machine to transferpower to an output member, the transmission selectively operative in oneof a plurality of operating range states includes monitoring operatorinputs to an accelerator pedal, determining a preferred operating pointof the powertrain based upon the operator inputs, determining apreferred operating range state of the transmission based upon thepreferred operating point, determining lead control signals for theengine and the transmission based upon the preferred operating point andthe preferred operating range state of the transmission, determiningimmediate control signals for the electric machine and the transmission,wherein the immediate control signals are based upon a lead periodcalibrated to a difference in control signal reaction times of theengine and the electric machine in order to effect changes to an actualelectric machine output substantially simultaneously with changes to anactual engine output, controlling operation of the engine based upon thelead control signals for the engine and the transmission, andcontrolling operation of the electric machine based upon the immediatecontrol signals for the electric machine and the transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an exemplary powertrain comprising atwo-mode, compound-split, electro-mechanical hybrid transmissionoperatively connected to an engine and first and second electricmachines, in accordance with the present disclosure;

FIG. 2 is a schematic block diagram of an exemplary distributed controlmodule system, in accordance with the present disclosure;

FIG. 3 graphically depicts reaction times of exemplary hybrid powertraincomponents to changes in torque request, in accordance with the presentdisclosure;

FIG. 4 demonstrates gear transition relationships for an exemplaryhybrid powertrain transmission, in particular as described in theexemplary embodiment of FIG. 1 and Table 1, in accordance with thepresent disclosure;

FIGS. 5-7 depict exemplary processes combining to accomplish anexemplary transmission shift, in accordance with the present disclosure;

FIG. 5 is a graphical representation of torque terms associated with aclutch through an exemplary transitional unlocking state;

FIG. 6 is a graphical representation of torque terms associated with aclutch through an exemplary transitional locking state;

FIG. 7 is a graphical representation of terms describing an exemplaryinertia speed phase of a transmission, in accordance with the presentdisclosure;

FIG. 8 is a graphical representation of an instance where a systemicrestraint is imposed upon an immediate control signal, temporarilyoverriding max\min values set by the control signal, in accordance withthe present disclosure;

FIG. 9 shows an exemplary control system architecture for controllingand managing torque and power flow in a powertrain system havingmultiple torque generative devices and residing in control modules inthe form of executable algorithms and calibrations, in accordance withthe present disclosure; and

FIG. 10 is a schematic diagram exemplifying data flow through a shiftexecution, describing more detail exemplary execution of the controlsystem architecture of FIG. 9 in greater detail, in accordance with thepresent disclosure.

DETAILED DESCRIPTION

Referring now to the drawings, wherein the showings are for the purposeof illustrating certain exemplary embodiments only and not for thepurpose of limiting the same, FIGS. 1 and 2 depict an exemplaryelectro-mechanical hybrid powertrain. The exemplary electro-mechanicalhybrid powertrain in accordance with the present disclosure is depictedin FIG. 1, comprising a two-mode, compound-split, electro-mechanicalhybrid transmission 10 operatively connected to an engine 14 and firstand second electric machines (‘MG-A’) 56 and (‘MG-B’) 72. The engine 14and first and second electric machines 56 and 72 each generate powerwhich can be transmitted to the transmission 10. The power generated bythe engine 14 and the first and second electric machines 56 and 72 andtransmitted to the transmission 10 is described in terms of inputtorques, referred to herein as T_(I), T_(A), and T_(B) respectively, andspeed, referred to herein as N_(I), N_(A), and N_(B), respectively.

The exemplary engine 14 comprises a multi-cylinder internal combustionengine selectively operative in several states to transmit torque to thetransmission 10 via an input shaft 12, and can be either aspark-ignition or a compression-ignition engine. The engine 14 includesa crankshaft (not shown) operatively coupled to the input shaft 12 ofthe transmission 10. A rotational speed sensor 11 monitors rotationalspeed of the input shaft 12. Power output from the engine 14, comprisingrotational speed and output torque, can differ from the input speed,N_(I), and the input torque, T_(I), to the transmission 10 due toplacement of torque-consuming components on the input shaft 12 betweenthe engine 14 and the transmission 10, e.g., a hydraulic pump (notshown) and/or a torque management device (not shown).

The exemplary transmission 10 comprises three planetary-gear sets 24, 26and 28, and four selectively engageable torque-transmitting devices,i.e., clutches C1 70, C2 62, C3 73, and C4 75. As used herein, clutchesrefer to any type of friction torque transfer device including single orcompound plate clutches or packs, band clutches, and brakes, forexample. A hydraulic control circuit 42, preferably controlled by atransmission control module (hereafter ‘TCM’) 17, is operative tocontrol clutch states. Clutches C2 62 and C4 75 preferably comprisehydraulically-applied rotating friction clutches. Clutches C1 70 and C373 preferably comprise hydraulically-controlled stationary devices thatcan be selectively grounded to a transmission case 68. Each of theclutches C1 70, C2 62, C3 73, and C4 75 is preferably hydraulicallyapplied, selectively receiving pressurized hydraulic fluid via thehydraulic control circuit 42.

The first and second electric machines 56 and 72 preferably comprisethree-phase AC machines, each including a stator (not shown) and a rotor(not shown), and respective resolvers 80 and 82. The motor stator foreach machine is grounded to an outer portion of the transmission case68, and includes a stator core with coiled electrical windings extendingtherefrom. The rotor for the first electric machine 56 is supported on ahub plate gear that is operatively attached to shaft 60 via the secondplanetary gear set 26. The rotor for the second electric machine 72 isfixedly attached to a sleeve shaft hub 66.

Each of the resolvers 80 and 82 preferably comprises a variablereluctance device including a resolver stator (not shown) and a resolverrotor (not shown). The resolvers 80 and 82 are appropriately positionedand assembled on respective ones of the first and second electricmachines 56 and 72. Stators of respective ones of the resolvers 80 and82 are operatively connected to one of the stators for the first andsecond electric machines 56 and 72. The resolver rotors are operativelyconnected to the rotor for the corresponding first and second electricmachines 56 and 72. Each of the resolvers 80 and 82 is signally andoperatively connected to a transmission power inverter control module(hereafter ‘TPIM’) 19, and each senses and monitors rotational positionof the resolver rotor relative to the resolver stator, thus monitoringrotational position of respective ones of first and second electricmachines 56 and 72. Additionally, the signals output from the resolvers80 and 82 are interpreted to provide the rotational speeds for first andsecond electric machines 56 and 72, i.e., N_(A) and N_(B), respectively.

The transmission 10 includes an output member 64, e.g. a shaft, which isoperably connected to a driveline 90 for a vehicle (not shown), toprovide output power, e.g., to vehicle wheels 93, one of which is shownin FIG. 1. The output power is characterized in terms of an outputrotational speed, N_(O) and an output torque, T_(O). A transmissionoutput speed sensor 84 monitors rotational speed and rotationaldirection of the output member 64. Each of the vehicle wheels 93, ispreferably equipped with a sensor 94 adapted to monitor wheel speed,V_(SS-WHL), the output of which is monitored by a control module of adistributed control module system described with respect to FIG. B, todetermine vehicle speed, and absolute and relative wheel speeds forbraking control, traction control, and vehicle acceleration management.

The input torques from the engine 14 and the first and second electricmachines 56 and 72 (T_(I), T_(A), and T_(B) respectively) are generatedas a result of energy conversion from fuel or electrical potentialstored in an electrical energy storage device (hereafter ‘ESD’) 74. TheESD 74 is high voltage DC-coupled to the TPIM 19 via DC transferconductors 27. The transfer conductors 27 include a contactor switch 38.When the contactor switch 38 is closed, under normal operation, electriccurrent can flow between the ESD 74 and the TPIM 19. When the contactorswitch 38 is opened electric current flow between the ESD 74 and theTPIM 19 is interrupted. The TPIM 19 transmits electrical power to andfrom the first electric machine 56 by transfer conductors 29, and theTPIM 19 similarly transmits electrical power to and from the secondelectric machine 72 by transfer conductors 31, in response to torquerequests to the first and second electric machines 56 and 72 to achievethe input torques T_(A) and T_(B). Electrical current is transmitted toand from the ESD 74 in accordance with whether the ESD 74 is beingcharged or discharged.

The TPIM 19 includes the pair of power inverters (not shown) andrespective motor control modules (not shown) configured to receive thetorque commands and control inverter states therefrom for providingmotor drive or regeneration functionality to meet the commanded motortorques T_(A) and T_(B). The power inverters comprise knowncomplementary three-phase power electronics devices, and each includes aplurality of insulated gate bipolar transistors (not shown) forconverting DC power from the ESD 74 to AC power for powering respectiveones of the first and second electric machines 56 and 72, by switchingat high frequencies. The insulated gate bipolar transistors form aswitch mode power supply configured to receive control commands. Thereis typically one pair of insulated gate bipolar transistors for eachphase of each of the three-phase electric machines. States of theinsulated gate bipolar transistors are controlled to provide motor drivemechanical power generation or electric power regenerationfunctionality. The three-phase inverters receive or supply DC electricpower via DC transfer conductors 27 and transform it to or fromthree-phase AC power, which is conducted to or from the first and secondelectric machines 56 and 72 for operation as motors or generators viatransfer conductors 29 and 31 respectively.

FIG. 2 is a schematic block diagram of the distributed control modulesystem. The elements described hereinafter comprise a subset of anoverall vehicle control architecture, and provide coordinated systemcontrol of the exemplary powertrain described in FIG. 1. The distributedcontrol module system synthesizes pertinent information and inputs, andexecutes algorithms to control various actuators to achieve controlobjectives, including objectives related to fuel economy, emissions,performance, drivability, and protection of hardware, includingbatteries of ESD 74 and the first and second electric machines 56 and72. The distributed control module system includes an engine controlmodule (hereafter ‘ECM’) 23, the TCM 17, a battery pack control module(hereafter ‘BPCM’) 21, and the TPIM 19. A hybrid control module(hereafter ‘HCP’) 5 provides supervisory control and coordination of theECM 23, the TCM 17, the BPCM 21, and the TPIM 19. A user interface(‘UI’) 13 is operatively connected to a plurality of devices throughwhich a vehicle operator controls or directs operation of theelectro-mechanical hybrid powertrain. The devices include an acceleratorpedal 113 (‘AP’) from which an operator torque request is determined, anoperator brake pedal 112 (‘BP’), a transmission gear selector 114(‘PRNDL’), and a vehicle speed cruise control (not shown). Thetransmission gear selector 114 may have a discrete number ofoperator-selectable positions, including the rotational direction of theoutput member 64 to enable one of a forward and a reverse direction.

The aforementioned control modules communicate with other controlmodules, sensors, and actuators via a local area network (hereafter‘LAN’) bus 6. The LAN bus 6 allows for structured communication ofstates of operating parameters and actuator command signals between thevarious control modules. The specific communication protocol utilized isapplication-specific. The LAN bus 6 and appropriate protocols providefor robust messaging and multi-control module interfacing between theaforementioned control modules, and other control modules providingfunctionality such as antilock braking, traction control, and vehiclestability. Multiple communications buses may be used to improvecommunications speed and provide some level of signal redundancy andintegrity. Communication between individual control modules can also beeffected using a direct link, e.g., a serial peripheral interface(‘SPI’) bus (not shown).

The HCP 5 provides supervisory control of the powertrain, serving tocoordinate operation of the ECM 23, TCM 17, TPIM 19, and BPCM 21. Basedupon various input signals from the user interface 13 and thepowertrain, including the ESD 74, the HCP 5 generates various commands,including: the operator torque request (‘T_(O) _(—) _(REQ)’), acommanded output torque (‘T_(CMD)’) to the driveline 90, an engine inputtorque request, clutch torques for the torque-transfer clutches C1 70,C2 62, C3 73, C4 75 of the transmission 10; and the torque requests forthe first and second electric machines 56 and 72, respectively. The TCM17 is operatively connected to the hydraulic control circuit 42 andprovides various functions including monitoring various pressure sensingdevices (not shown) and generating and communicating control signals tovarious solenoids (not shown) thereby controlling pressure switches andcontrol valves contained within the hydraulic control circuit 42.

The ECM 23 is operatively connected to the engine 14, and functions toacquire data from sensors and control actuators of the engine 14 over aplurality of discrete lines, shown for simplicity as an aggregatebi-directional interface cable 35. The ECM 23 receives the engine inputtorque request from the HCP 5. The ECM 23 determines the actual engineinput torque, T_(I), provided to the transmission 10 at that point intime based upon monitored engine speed and load, which is communicatedto the HCP 5. The ECM 23 monitors input from the rotational speed sensor11 to determine the engine input speed to the input shaft 12, whichtranslates to the transmission input speed, N_(I). The ECM 23 monitorsinputs from sensors (not shown) to determine states of other engineoperating parameters including, e.g., a manifold pressure, enginecoolant temperature, ambient air temperature, and ambient pressure. Theengine load can be determined, for example, from the manifold pressure,or alternatively, from monitoring operator input to the acceleratorpedal 113. The ECM 23 generates and communicates command signals tocontrol engine actuators, including, e.g., fuel injectors, ignitionmodules, and throttle control modules, none of which are shown.

The TCM 17 is operatively connected to the transmission 10 and monitorsinputs from sensors (not shown) to determine states of transmissionoperating parameters. The TCM 17 generates and communicates commandsignals to control the transmission 10, including controlling thehydraulic control circuit 42. Inputs from the TCM 17 to the HCP 5include estimated clutch torques for each of the clutches, i.e., C1 70,C2 62, C3 73, and C4 75, and rotational output speed, N_(O), of theoutput member 64. Other actuators and sensors may be used to provideadditional information from the TCM 17 to the HCP 5 for controlpurposes. The TCM 17 monitors inputs from pressure switches (not shown)and selectively actuates pressure control solenoids (not shown) andshift solenoids (not shown) of the hydraulic control circuit 42 toselectively actuate the various clutches C1 70, C2 62, C3 73, and C4 75to achieve various transmission operating range states, as describedhereinbelow.

The BPCM 21 is signally connected to sensors (not shown) to monitor theESD 74, including states of electrical current and voltage parameters,to provide information indicative of parametric states of the batteriesof the ESD 74 to the HCP 5. The parametric states of the batteriespreferably include battery state-of-charge, battery voltage, batterytemperature, and available battery power, referred to as a range P_(BAT)_(—) _(MIN) to P_(BAT) _(—) _(MAX).

Each of the control modules ECM 23, TCM 17, TPIM 19 and BPCM 21 ispreferably a general-purpose digital computer comprising amicroprocessor or central processing unit, storage mediums comprisingread only memory (‘ROM’), random access memory (‘RAM’), electricallyprogrammable read only memory (‘EPROM’), a high speed clock, analog todigital (‘A/D’) and digital to analog (‘D/A’) circuitry, andinput/output circuitry and devices (‘I/O’) and appropriate signalconditioning and buffer circuitry. Each of the control modules has a setof control algorithms, comprising resident program instructions andcalibrations stored in one of the storage mediums and executed toprovide the respective functions of each computer. Information transferbetween the control modules is preferably accomplished using the LAN bus6 and SPI buses. The control algorithms are executed during preset loopcycles such that each algorithm is executed at least once each loopcycle. Algorithms stored in the non-volatile memory devices are executedby one of the central processing units to monitor inputs from thesensing devices and execute control and diagnostic routines to controloperation of the actuators, using preset calibrations. Loop cycles areexecuted at regular intervals, for example each 3.125, 6.25, 12.5, 25and 100 milliseconds during ongoing operation of the powertrain.Alternatively, algorithms may be executed in response to the occurrenceof an event.

The exemplary powertrain selectively operates in one of severaloperating range states that can be described in terms of an engine statecomprising one of an engine on state (‘ON’) and an engine off state(‘OFF’), and a transmission state comprising a plurality of fixed gearsand continuously variable operating modes, described with reference toTable 1, below.

TABLE 1 Engine Transmission Operating Applied Description State RangeState Clutches MI_Eng_Off OFF EVT Mode I C1 70 MI_Eng_On ON EVT Mode IC1 70 FG1 ON Fixed Gear Ratio 1 C1 70 C4 75 FG2 ON Fixed Gear Ratio 2 C170 C2 62 MII_Eng_Off OFF EVT Mode II C2 62 MII_Eng_On ON EVT Mode II C262 FG3 ON Fixed Gear Ratio 3 C2 62 C4 75 FG4 ON Fixed Gear Ratio 4 C2 62C3 73

Each of the transmission operating range states is described in thetable and indicates which of the specific clutches C1 70, C2 62, C3 73,and C4 75 are applied for each of the operating range states. A firstcontinuously variable mode, i.e., EVT Mode I, or MI, is selected byapplying clutch C1 70 only in order to “ground” the outer gear member ofthe third planetary gear set 28. The engine state can be one of ON(‘MI_Eng_On’) or OFF (‘MI_Eng_Off’). A second continuously variablemode, i.e., EVT Mode II, or MII, is selected by applying clutch C2 62only to connect the shaft 60 to the carrier of the third planetary gearset 28. The engine state can be one of ON (‘MII_Eng_On’) or OFF(‘MII_Eng_Off’). For purposes of this description, when the engine stateis OFF, the engine input speed is equal to zero revolutions per minute(‘RPM’), i.e., the engine crankshaft is not rotating. A fixed gearoperation provides a fixed ratio operation of input-to-output speed ofthe transmission 10, i.e., N_(I)/N_(O), is achieved. A first fixed gearoperation (‘FG1’) is selected by applying clutches C1 70 and C4 75. Asecond fixed gear operation (‘FG2’) is selected by applying clutches C170 and C2 62. A third fixed gear operation (‘FG3’) is selected byapplying clutches C2 62 and C4 75. A fourth fixed gear operation (‘FG4’)is selected by applying clutches C2 62 and C3 73. The fixed ratiooperation of input-to-output speed increases with increased fixed gearoperation due to decreased gear ratios in the planetary gears 24, 26,and 28. The rotational speeds of the first and second electric machines56 and 72, N_(A) and N_(B) respectively, are dependent on internalrotation of the mechanism as defined by the clutching and areproportional to the input speed measured at the input shaft 12.

In response to operator input via the accelerator pedal 113 and brakepedal 112 as captured by the user interface 13, the HCP 5 and one ormore of the other control modules determine the commanded output torque,T_(CMD), intended to meet the operator torque request, T_(O) _(—)_(REQ), to be executed at the output member 64 and transmitted to thedriveline 90. Final vehicle acceleration is affected by other factorsincluding, e.g., road load, road grade, and vehicle mass. The operatingrange state is determined for the transmission 10 based upon a varietyof operating characteristics of the powertrain. This includes theoperator torque request, communicated through the accelerator pedal 113and brake pedal 112 to the user interface 13 as previously described.The operating range state may be predicated on a powertrain torquedemand caused by a command to operate the first and second electricmachines 56 and 72 in an electrical energy generating mode or in atorque generating mode. The operating range state can be determined byan optimization algorithm or routine, initiated for example within ahybrid strategic control module of the HCP 5, which determines optimumsystem efficiency based upon operator demand for power, battery state ofcharge, and energy efficiencies of the engine 14 and the first andsecond electric machines 56 and 72. The control system manages torqueinputs from the engine 14 and the first and second electric machines 56and 72 based upon an outcome of the executed optimization routine, andsystem efficiencies are optimized thereby, to manage fuel economy andbattery charging. Furthermore, operation can be determined based upon afault in a component or system. The HCP 5 monitors the torque-generativedevices, and determines the power output from the transmission 10required to achieve the desired output torque to meet the operatortorque request. As should be apparent from the description above, theESD 74 and the first and second electric machines 56 and 72 areelectrically-operatively coupled for power flow therebetween.Furthermore, the engine 14, the first and second electric machines 56and 72, and the electro-mechanical transmission 10 aremechanically-operatively coupled to transmit power therebetween togenerate a power flow to the output member 64.

As discussed above, managing output torque in order to maintaindrivability is a priority in controlling a hybrid powertrain. Any changein torque in response to a change in output torque request appliedthrough the transmission results in a change to the output torqueapplied to the driveline, thereby resulting in a change in propellingforce to the vehicle and a change in vehicle acceleration. The change intorque request can come from operator input, such a pedal positionrelating an operator torque request, automatic control changes in thevehicle, such as cruise control or other control strategy, or enginechanges in response to environmental conditions, such as a vehicleexperiencing an uphill or downhill grade. By controlling changes tovarious input torques applied to a transmission within a hybridpowertrain, abrupt changes in vehicle acceleration can be controlled andminimized in order to reduce adverse effects to drivability.

As is known by one having ordinary skill in the art, any control systemincludes a reaction time. Changes to a powertrain operating point,comprising the speeds and torques of the various components to thepowertrain required to achieve the desired vehicle operation, are drivenby changes in control signals. These control signal changes act upon thevarious components to the powertrain and create reactions in eachaccording to their respective reaction times. Applied to a hybridpowertrain, any change in control signals indicating a new torquerequest, for instance, as driven by a change in operator torque requestor as required to execute a transmission shift, creates reactions ineach affected torque generating device in order to execute the requiredchanges to respective input torques. Changes to input torque suppliedfrom an engine are controlled by an engine torque request setting thetorque generated by the engine, as controlled, for example, through anECM. Reaction time within an engine to changes in torque request to anengine is impacted by a number of factors well known in the art, and theparticulars of a change to engine operation depend heavily on theparticulars of the engine employed and the mode or modes of combustionbeing utilized. In many circumstances, the reaction time of an engine tochanges in torque request will be the longest reaction time of thecomponents to the hybrid drive system. Reaction time within an electricmachine to changes in torque request include time to activate anynecessary switches, relays, or other controls and time to energize orde-energize the electric machine with the change in applied electricalpower.

FIG. 3 graphically depicts reaction times of exemplary hybrid powertraincomponents to changes in torque request, in accordance with the presentdisclosure. Components to an exemplary hybrid powertrain systemincluding an engine and two electric machines are exemplified. Torquerequests and resulting changes in input torque produced by each torquegenerating device are illustrated. As described above, the data showsthat electric machines quickly respond to changes in torque requests,whereas the engine follows changes in torque requests more slowly.

A method is disclosed wherein reactions times of the engine and of theelectric machine or machines within a hybrid powertrain are utilized tocontrol in parallel an lead immediate torque request, controlling theengine, and an immediate torque request, controlling the electricmachines, the torque requests being coordinated by respective reactiontimes in order to substantially effect simultaneous changes to inputtorque.

Because, as discussed above, changes to input torque from the engine areknown to involve consistently longer reactions times than changes toinput torque from an electric machine, an exemplary embodiment of thedisclosed method can implement changes in torque request to the engineand the electric machine, acting in parallel as described above,including a lead period to the more quickly reacting device, theelectric motor. This lead period may be developed experimentally,empirically, predictively, through modeling or other techniques adequateto accurately predict engine and electric machine operation, and amultitude of lead periods might be used by the same hybrid powertrain,depending upon different engine settings, conditions, operating andranges and vehicle conditions. An exemplary equation that can be used inconjunction with test data or estimates of device reaction times tocalculate lead period in accordance with the present disclosure includesthe following:T _(Lead) =T _(Lead Reaction) −T _(Immediate Reaction)T_(Lead) equals the lead period for use in methods described herein.This equation assumes that two torque producing devices are utilized.T_(Lead Reaction) represents the reaction time of the device with thelonger reaction time, and T_(Immediate Reaction) represents the reactiontime of the device with the shorter reaction time. If a different systemis utilized, comprising for example, an engine with a long lead period,a first electric machine with an intermediate lead period, and a secondelectric machine with a short lead period, lead periods can be developedcomparing all of the torque generating devices. In this exemplarysystem, if all three torque generating devices are involved, two leadperiods, one for the engine as compared to each of the electricmachines, will be utilized to synchronize the responses in each of thedevices. The same system at a different time might be operating with theengine off and disengaged from the transmission, and a lead periodcomparing the first electric machine and the second electric machinewill be utilized to synchronize the responses in the two electricmachines. In this way, a lead period can be developed coordinatingreaction times between various torque generating devices can bedeveloped.

One exemplary method to utilize lead periods to implement paralleltorque requests to distinct torque generating devices in order to effectsubstantially simultaneous changes to output torque in response to achange in operator torque request includes issuing substantiallyimmediately a change to the engine torque immediate request, initiatingwithin the engine a change to a new engine output torque. This newengine output torque, in conjunction with the electric motor operatingstate, is still managed by the HCP in order to provide some portion ofthe total input torque to the transmission required to propel thevehicle. From the point that the engine torque immediate requestchanges, the lead period expires, described above taking into accountthe differences in reaction times between the engine and the electricmachine. After the lead period, a change to torque requests issued tothe electric machine or machines, managed by the HCP in order to fulfilla portion of the operator torque request, is executed, and the electricmachine changes the electric machine operating state, and as describedabove, the changes to the input torques provided by the engine and theelectric machine change substantially simultaneously.

As described in the disclosed method above, engine torque immediaterequests and torque requests to an electric machine are disclosed foruse in parallel to control distinct torque generative devices withdifferent reaction times to reaction to changes in operator torquerequest. Changes in operator torque request can include a simple changein desired output torque within a particular transmission operatingrange state, or changes in operator torque request can be required inconjunction with a transmission shift between different operating rangestates. Changes to operator torque requests in conjunction with atransmission shift are more complex than changes contained within asingle operating range state because torques and shaft speeds of thevarious hybrid powertrain components must be managed in order totransition torque applied from a first clutch and to a second previouslynot applied clutch without the occurrence of slip, as described above.

Shifts within a transmission, such as the exemplary transmission of FIG.1, frequently involve unloading a first clutch, transitioning through aninertia speed phase state, and subsequently loading a second clutch.Within the transmission of a conventionally powered vehicle utilizing anengine only, the change within a transmission from one fixed gear stateto another fixed gear state frequently includes unloading a firstclutch, allowing the vehicle to briefly coast, and then loading a secondclutch. However, as described in relation to FIG. 1 and Table 1, above,clutches within a hybrid powertrain transmission are frequently appliedin pairs or groups, and a shift within the transmission can involve onlyunloading one of the applied clutches and subsequently loading anotherclutch while maintaining engagement of a third clutch throughout theshift. FIG. 4 demonstrates gear transition relationships for anexemplary hybrid powertrain transmission, in particular as described inthe exemplary embodiment of FIG. 1 and Table 1, in accordance with thepresent disclosure. N_(I) is plotted against N_(O). At any fixed gearstate, N_(O) is determined by the corresponding N_(I) along the fixedgear state plots. Operation in either EVT Mode I or EVT Mode II, whereina continuously variable gear ratio is utilized to power from a fixedinput speed can take place in the respective zones illustrated on thegraph. Clutch states, C1-C4, as described in the exemplary embodiment ofFIG. 1, are described in Table 1. For instance, operation in a secondfixed gear state requires clutches C1 and C2 to be applied or loaded andclutches C3 and C4 to be not applied or unloaded. While FIG. 4 describesgear transitions possible in the exemplary powertrain illustrated inFIG. 1, it will be appreciated by one having ordinary skill in the artthat such a description of gear transitions is possible for anytransmission of a hybrid powertrain, and the disclosure is not intendedto be limited to the particular embodiment described herein.

FIG. 4 can describe operation of an exemplary system in a fixed gearstate or EVT mode, as described above, and it can also be used todescribe shift transitions between the various transmission operatingrange states. The areas and plots on the graph describe operation of theoperating range states through transitions. For example, transitionsbetween fixed gear states within an EVT mode region require transitoryoperation in the EVT mode between the fixed gear states. Similarly,transition from EVT Mode I to EVT Mode II requires a transition throughthe second fixed gear state, located at the boundary between the twomodes.

In accordance with FIGS. 1 and 4 and Table 1, an exemplary transmissionshift from a third fixed gear state to a fourth fixed gear state isfurther described. Referring to FIG. 4, both the beginning and thepreferred operating range states exist within the area of EVT Mode II.Therefore, a transition from the third gear state to the fourth gearstate requires first a shift from the third fixed gear state to EVT ModeII and then a shift from EVT Mode II to the fourth fixed gear state.Referring to Table 1, a hybrid powertrain transmission, beginning in athird fixed gear state, will have clutches C2 and C4 applied. Table 1further describes operation in EVT Mode II, the destination of the firstshift, to include clutch C2 applied. Therefore, a shift from the thirdfixed gear state to EVT Mode II requires clutch C4 to be changed from anapplied to a not applied state and requires that clutch C2 remainapplied. Additionally, Table 1 describes operation in the fourth fixedgear mode, the destination of the second shift, wherein clutches C2 andC3 are applied. Therefore, a shift from EVT Mode II to the fourth fixedgear state requires clutch C3 to be applied and loaded and requires thatclutch C2 remain applied. Therefore, clutches C4 and C3 are transitionedthrough the exemplary shift, while clutch C2 remains applied andtransmitting torque to the driveline throughout the shift event.

Applied to the methods disclosed herein, changes in input torque througha transmission shift can be optimized to reduce negative effects todrivability by coordinating signal commands to various torque generativedevices based upon reaction times of the various components. Asdescribed above, many transmission shifts can be broken down into threephases: a first torque phase, during which an initially applied clutchis changed from a torque-bearing, locked, and synchronized clutch stateto an unlocked and desynchronized clutch state; an inertia speed phase,during which affected clutches are unlocked and in transitional states;and a second torque phase, during which a second previously not appliedclutch is changed from an unlocked and desynchronized clutch state to atorque-bearing, locked, and synchronized clutch state. Asaforementioned, clutch slip is preferably avoided throughouttransmission shifts to avoid adverse effects on drivability, and clutchslip is created when reactive torque applied across a clutch exceeds theactual capacity torque of the clutch. Therefore, within a transmissionshift event, input torques must be managed in relation to the actualcapacity torque of the currently applied clutch, such that thetransmission shift can be accomplished without the occurrence of slip.

While a process can be utilized to perform necessary steps in a clutchloading or unloading event in sequence, with the capacity torque of theclutch being maintained in excess of reactive torques, time involved inan unlocking transition is also important to drivability. Therefore, itis advantageous to perform associated torque requests and clutchcapacity commands in parallel while still acting to prevent slip. Suchparallel implementation of control changes intending to effect clutchstate changes associated with a transmission shift preferably occur inas short of a time-span as possible. Therefore, coordination of capacitytorque within the clutches involved in the transmission shift to thetorque requests, both to the engine and to the electric machine, asdescribed in the exemplary embodiment above, is also important tomaintaining drivability through a transmission shift. FIGS. 5-7 depictexemplary processes combining to accomplish an exemplary transmissionshift, in accordance with the present disclosure.

FIG. 5 is a graphical representation of torque terms associated with aclutch through an exemplary transitional unlocking state, in accordancewith the present disclosure. Lines illustrated at the left extreme ofthe graph depict clutch operation in a locked state. The graph depictsclutch command torque by a clutch control system and a resultingestimated capacity torque. Capacity torque in a clutch resulting from acommand torque is a result of many factors, including available clampingpressure, design and conditional factors of the clutch, reaction time inthe clutch to changes in the clutch control system. As demonstrated inthe exemplary data of the graph in the initial locked region, it isknown to command a torque to a locked clutch in excess of the clutchcapacity and allow the other factors affecting the clutch to determinethe resulting clutch capacity. Also at the left extreme of the graphdepicting clutch operation in a locked state, estimated reactive torqueapplied to the clutch as a result of input torque from the engine andelectric machine torques is depicted. At the time labeled “InitiateUnlocking State”, logic within the clutch control system or the TCM,having determined a need to transition the clutch from locked tounlocked states, changes the command torque to some level lower than thecapacity torque but still higher than the reactive torque currentlyapplied to the clutch. At this point, mechanisms within the clutchcontrol system, for example, variable pressure control solenoids withinan exemplary hydraulic clutch control system, change settings tomodulate the clamping force within the clutch. As a result, capacitytorque of the clutch begins to change as the clamping force applied tothe clutch changes. As discussed above, the clutch reacts to a change incommand torque over a reaction time, and reaction time for a particularclutch will depend upon the particulars of the application. In theexemplary graph of FIG. 5, capacity torque reacts to a reduction incommand torque and begins to reduce accordingly.

As mentioned above, during the same unlocking state, reactive torqueresulting from input torque and electric machine torques must also beunloaded from the clutch. Undesirable slip results if the reactivetorque is not maintained below the capacity torque throughout theunlocking state. Upon initiation of the unlocking state, atsubstantially the same point on FIG. 5 where the capacity torque isreduced to initiate the unlocking state, limits are initiated andimposed upon input torques from the engine and the electric machine inorder to accomplish a ramping down of each to zero. As described in themethod disclosed herein and in exemplary embodiments described above,changes to limits including a engine torque immediate request and animmediate torque request are executed in a coordinated process,implementing a lead period calibrated to the reaction times of thevarious torque providing devices, such that the resulting input torquesfrom the devices are reduced substantially simultaneously. FIG. 5illustrates a method to perform this coordinated change to torquerequests by imposing limits upon torque requests in the form of a clutchreactive torque lead immediate minimum and maximum constraining theengine torque immediate request and a clutch reactive torque immediateminimum and maximum constraining the torque request to the electricmachine. These maximum reactive torque values represent the maximumtorque that is permitted to be commanded from each torque providingdevice: the actual engine torque immediate request and the actualimmediate torque request can be less than the maximum reactive torquevalues, but as the maximum values reduce, so the actual torque requestvalues will also eventually reduce. The input torques from the engineand electric machine together provide, each up to the defined maximumvalues, some portion of the overall input torques, with the portion ofeach being controlled by the HCP. As a result of the calibrated leadperiod, both the clutch reactive torque lead immediate minimum andmaximum and the clutch reactive torque immediate minimum and maximumreduce applied reactive torque to the clutch at substantially the sametime, resulting in the reduction to the actual clutch reactive torque asillustrated in FIG. 5. As will be appreciated by one having ordinaryskill in the art, other safeguards will additionally need to be utilizedto ensure that the capacity torque remains in excess of the reactivetorque throughout the unloading process. Many such methods arecontemplated, and an exemplary set of terms which might be used aredepicted on FIG. 5. For instance, a calibrated offset term can be usedto ensure that the command setting the clutch capacity remains in excessof the actual clutch reactive torque until the actual torque passesbelow some threshold. An exemplary threshold for such a purpose isdefined in FIG. 5 as the calibrated threshold for reactive torque. Inmaintaining this capacity torque request above the actual clutchreactive torque, and remembering that all devices include a reactiontime to request changes, including the clutch clamping mechanism, thedelay in the change to capacity torque in response to clutch commandchanges in combination with this offset term will maintain the capacitytorque in excess of the actual clutch reactive torque. Additionally,another threshold, a calibrated threshold for torque estimate, can beused to define the end of the torque phase. For instance, if an estimateof the clutch torque capacity, as determined by an algorithm modelingclutch operation, stays below this threshold through a calibrated periodof time, then the clutch can be determined to be in an unlocked state.

FIG. 6 is a graphical representation of torque terms associated with aclutch through an exemplary transitional locking state, in accordancewith the present disclosure. As described above, within manytransmission shift events, a second clutch is synchronized and locked,and torque is applied to the clutch. Lines illustrated at the leftextreme of the graph depict clutch operation in an unlocked state. Theinitiation of locking state requires a series of subordinate commandsnecessary to transition the clutch from an unlocked state to a lockedstate. As described above in relation to a transition to a second torquephase within a transmission shift, the clutch, including the shaftconnected to the oncoming torque providing shafts and the shaftconnected to the output member, must be synchronized. Once the clutchconnective surfaces attached to these shafts have been attenuated andare moving at the same rotational velocity, clamping force can begin tobe applied to the clutch to bring the clutch to a locked state and beginincreasing the capacity torque of the clutch. As described above withregards to avoiding slip during a torque phase, clutch capacity must beincreased before reactive torque to the clutch can be increased. Inorder to enable the application of input torques resulting in a reactivetorque across the clutch as rapidly as possible, an increase in clutchcapacity can be commanded anticipatorily to achieve an initial increasein clutch capacity coincident with the clutch reaching a locked state.Reactive torques, taking into account reaction times by utilizing a leadperiod by the method disclosed herein, can then be timely commanded witha short lag to follow increasing clutch capacity torque. An exemplaryembodiment of this method, acting in reverse of the limits imposed totorque requests as described in FIG. 5, imposes limits upon the torquerequests which can be issued to the engine and to the electric machineaccording to a calibrated ramp rate, selected to avoid slip. As depictedin FIG. 6, an clutch reactive torque immediate minimum and maximumacting as a constraint upon electric machine torque requests isincreased after a calibrated lead period from the initiation of anincreasing clutch reactive torque lead immediate minimum and maximumacting as a constraint upon engine torque requests. By utilizing thelead period, the increase in input torques from the engine and theelectric machine increase reactive torque applied to the clutchsubstantially simultaneously, according to the methods disclosed herein.As the limits upon the torque generating devices are lifted according tothe calibrated ramp rate applied to each limit, the HCP can command theengine and the electric machine to fulfill a portion of the reactivetorque required from the clutch, each up to the respective maximum. Inthis way, torque requests to the engine and the electric machine arecoordinated in order to compensate for reaction times in order toincrease input torques from each substantially simultaneously through ashift event.

The calibrated ramp rate utilized in the above exemplary transmissionshift is a selected value which will adjust input torque levels to thedesired range quickly, but also will stay below the capacity torque forthe clutch so as to avoid slip. The ramp rate may be developedexperimentally, empirically, predictively, through modeling or othertechniques adequate to accurately predict engine and electric machineoperation, and a multitude of ramp rates might be used by the samehybrid powertrain, depending upon different engine settings, conditions,or operating ranges and behavior of the control system actuating theclutch capacity torque. The ramp rate used to decrease input torques inan unlocking event can but need not be an inverse of the ramp rate usedto increase input torques in a locking event. Similarly, the lead periodused to coordinate input torques can but need not be the same time spanvalue utilized in both transmission transitional states and can bevaried according to particular behaviors of a vehicle and itscomponents.

As described above, during a transmission shift, for example, betweentwo fixed gear states as defined in the exemplary transmission describedabove, the transmission passes through an inertia speed phase between afirst torque phase and a second torque phase. During this inertia speedphase, the originally applied clutch and the clutch to be applied are inan unlocked state, and the input is initially spinning with a rotationalvelocity that was shared across the first clutch just prior to becomingunsynchronized. In order to accomplish synchronization within the secondclutch to be applied and loaded in the second torque phase, inputs to beconnected to the second clutch must change input speed to match thedriveline attached through the transmission at some new gear ratio. Anumber of methods are known in the art to accomplish thissynchronization. However, within a shift in a hybrid powertraintransmission, shifts usually occur through range operating state whereat least one clutch is still applied while another clutch is in aninertia speed phase. This means that changes to the various torquegenerative devices required to create synchronization in the input speedand output speed of the second clutch still impact vehicle performancein the inertia speed phase through the still applied clutch. Therefore,the methods described herein to utilize a lead period to effect changesto input torques substantially simultaneously can additionally presentadvantages to drivability can continue to be utilized through an inertiaspeed phase.

An exemplary method to accomplish this synchronization through aninertia speed phase of a transmission shift is graphically depicted inFIG. 7, in accordance with the present disclosure. The effects of thetransmission shift upon two terms descriptive of the shifting processare illustrated in two sections with a common timescale. The top sectiondepicts the input speed, or the rotational velocity of an input shaftattached to a torque generating device, of a shaft initially connectedthrough the first, initially applied clutch. The upper dotted linerepresents the velocity profile of the input speed while the firstclutch is in a locked state before initiation of the shift. The bottomdotted line represents the velocity profile of the input speed that mustbe achieved to synchronize the input speed with the output speed of thesecond clutch. The transition between the two dotted lines representsthe change to input speed that must take place to accomplish the shift.The bottom section of FIG. 7 depicts input acceleration, or a derivativewith respect to time of the input speed. Input acceleration is describedin this case as the input acceleration immediate or the accelerationprofile driven with a relatively quick reaction time by an electricmachine or machines, and the term closely tracks actual inputacceleration. The input acceleration immediate shows the change in therate of speed which must be accomplished in order to transition theinput speed from an initial input speed at the synchronous state withthe first clutch to a target input speed at the synchronous state withthe second clutch. The initial flat portion describes the accelerationwith which the input speed is increased before the initiation of theshift, and this constant value reflects the slope of the input speed inthe left portion of the top section of the FIG. 7. At the time of theinitiation of the shift, based upon operator input such as pedalposition and algorithms within the transmission control system,including determining a preferred operating range state, a determinationis made regarding target input speed that will be required to achievesynchronization and the target input acceleration profile required toaccomplish the shift. An input acceleration rate, calculated to supporta target acceleration rate after the shift is completed, can be termedan input acceleration lead predicted and describes the inputacceleration that needs to exist after the inertia speed phase iscompleted. The input acceleration lead immediate is predicted through analgorithm factoring in operator requested torque, the preferredoperating range state being transitioned to, and other relevantvariables. Because, as described in the top portion of FIG. 7, the inputspeed must be changed through the inertia speed phase to accomplish theshift and because the input acceleration describes the rate of change ofthe input speed, the input acceleration of the device being controlledduring the inertia speed phase must reflect the input speed change to beaccomplished through the inertia speed phase. In the exemplary datadisplayed in FIG. 7, wherein the input speed needs to be reduced toaccomplish the transmission shift, the input acceleration of the devicenecessarily must change to a negative value representing the change ininput speed. Once the input speed has been reduced to a level enablingtransition to the target input speed needed for synchronizing the inputand output speeds, the input acceleration changes to match the inputacceleration lead predicted. In this way, input speed and inputacceleration can be controlled through an inertia speed phase to match atarget input speed and target input acceleration necessary to achieve asmooth transmission shift.

As described above, a transmission shift in a hybrid powertraintransmission requires transition between operating range states, whereinan inertia speed phase must be accomplished as described above, while atleast one clutch is still applied and transferring torque from thetorque producing devices to the driveline. Changes to input torques,driven by torque requests to the various torque generating devices, mustaccomplish both the required input speed and input acceleration changesand maintain drivability throughout the inertia speed phase. Therefore,the methods described herein to utilize a lead period to effect changesto input torques substantially simultaneously can be utilized through aninertia speed phase to effect torque request changes to the varioustorque producing devices in order to effect substantially simultaneouschanges to the input torques. FIG. 7 illustrates coordinating torqueproducing device reaction times, and a lead period calibrated to thedifference in the related reaction times, to improve drivability in atransmission shift. An engine, as described above, includes the greaterreaction time among torque generating devices. In order to adjust theinput speed and input acceleration as quickly as possible to achieve thetarget speed and acceleration values for the shift, an inputacceleration lead immediate is predicted through an algorithm. Thisinput acceleration lead immediate includes the reaction time of theengine to changes in torque requests, and profiles the most rapid changein input speed and input acceleration in the lead device that can beaccomplished to reach the target values. This rapid change in inputspeed must include the aforementioned reaction time in the engine tochanges in torque requests and the time the engine will take toaccelerate or decelerate through the input acceleration lead immediate.As depicted in FIG. 7, the input acceleration lead immediate, inanticipation of a pending shift, can initiate requisite commands to theengine in anticipation of the inertia speed phase, as the resultinginput torque from the engine will not begin to reduce until later, dueto the relatively long engine reaction time. Once the input accelerationlead immediate has been determined, an input acceleration immediate,following the input acceleration lead immediate by a lead period,calibrated to reaction times as described above, can be utilized tocontrol the electric machine to match changes in input speed and inputacceleration at substantially the same time as the response from theengine. In this way, the engine and the electric machines aresubstantially synchronized in affecting the target input speed andtarget acceleration.

The above methods describe cases in which a transmission is operatingwith a clutch or clutches engaged and with a torque being applied fromat least one input torque to either an output torque or between torquegenerating devices. However, a neutral operating range state is knownwherein all clutches are unlocked and no torque is being applied throughthe transmission. One having ordinary skill in the art will appreciatethat for various reasons, either the engine or an electric machine canbe set to an idle or operational state in a neutral condition, and thatportions of the transmission attached to the running device can continueto spin. In such a neutral operating state, such portions of thetransmission can apply little resistance to the spinning device and canquickly accelerate to a high rotational speed. Such portions of thetransmission rotating at high speeds can cause a variety of issues,including noise and vibrations issues, damage to the spinning parts, orthe spinning parts, storing kinetic energy, can cause a perceptible jerkin the transmission if subsequently connected through a clutch. Theabove methods, monitoring portions of the powertrain and issuing leadand immediate control signals to the torque generating devices in orderto maintain control over the torques and speeds of the various portionsof the powertrain, can be applied in the neutral operating range stateto monitor speed of various components, monitored or predicted as aclutch slip acceleration lead predicted and by imposing limits uponclutch slip acceleration in a lead control signal as a clutch slipacceleration lead immediate and an immediate control signal as a clutchslip acceleration immediate. Operated in this way, a powertrain can becontrolled through a neutral operating range state, maintaining speed ofvarious portions of the transmission within a preferred range.

The above methods describe torque management processes as a comparisonof positive values. It will be appreciated by one having ordinary skillin the art that clutch torques are described as positive and negativetorques, signifying torques applied in one rotational direction or theother. The above method can be used in either positive or negativetorque applications, where the magnitudes of the torques are modulatedin such a way that the magnitude of the applied reactive torque does notexceed the magnitude of the torque capacity for a particular clutch. Oneparticular corollary to minimum and maximum reactive torque values isillustrated in FIG. 8. FIG. 8 graphically illustrates an instance inwhich an input acceleration lead immediate has been determined forengine control through an inertia speed phase, and additionally, acorresponding input acceleration immediate has been determined forelectric machine control through the inertia speed phase. In an instancewhere negative input acceleration or deceleration is occurring to theengine in an inertia speed phase, this condition is most commonly aninstance where the engine is simply being allowed to slow down byinternal frictional and pumping forces within the engine. However, whenan electric machine is decelerating, this condition is most commonlyaccomplished with the electric machine still under power, or conversely,operating in a regeneration mode. Because the electric machine is stilloperating under system control and with implications with the rest ofvehicle's systems, the motor is still subject to systemic restraints,for instance, battery power available to drive the motor. FIG. 8 imposessuch a systemic restraint in the minimum input acceleration constraint.Where such a restraint interferes with the input acceleration immediate,algorithms within the electric machine control system modify the inputacceleration immediate to accommodate the constraint. Once theconstraint no longer limits electric machine operation within the inputacceleration immediate, the algorithm operates to recover the inputacceleration to the effect the desired changes to the input speed.

FIG. 9 shows a control system architecture for controlling and managingtorque and power flow in a powertrain system having multiple torquegenerative devices, described hereinbelow with reference to the hybridpowertrain system shown in FIGS. 1 and 2, and residing in theaforementioned control modules in the form of executable algorithms andcalibrations. The control system architecture can be applied to anypowertrain system having multiple torque generative devices, including,e.g., a hybrid powertrain system having a single electric machine, ahybrid powertrain system having multiple electric machines, andnon-hybrid powertrain systems.

The control system architecture of FIG. 9 depicts a flow of pertinentsignals through the control modules. In operation, the operator inputsto the accelerator pedal 113 and the brake pedal 112 are monitored todetermine the operator torque request (‘T_(O) _(—) _(REQ)’). Operationof the engine 14 and the transmission 10 are monitored to determine theinput speed (‘N_(I)’) and the output speed (‘N_(O)’). A strategicoptimization control scheme (‘Strategic Control’) 310 determines apreferred input speed (‘N_(I) _(—) _(DES)’) and a preferred engine stateand transmission operating range state (‘Hybrid Range State Des’) basedupon the output speed and the operator torque request, and optimizedbased upon other operating parameters of the hybrid powertrain,including battery power limits and response limits of the engine 14, thetransmission 10, and the first and second electric machines 56 and 72.The strategic optimization control scheme 310 is preferably executed bythe HCP 5 during each 100 ms loop cycle and each 25 ms loop cycle.

The outputs of the strategic optimization control scheme 310 are used ina shift execution and engine start/stop control scheme (‘Shift Executionand Engine Start/Stop’) 320 to command changes in the transmissionoperation (‘Transmission Commands’) including changing the operatingrange state. This includes commanding execution of a change in theoperating range state if the preferred operating range state isdifferent from the present operating range state by commanding changesin application of one or more of the clutches C1 70, C2 62, C3 73, andC4 75 and other transmission commands. The present operating range state(‘Hybrid Range State Actual’) and an input speed profile (‘N_(I) _(—)_(PROF)’) can be determined. The input speed profile is an estimate ofan upcoming input speed and preferably comprises a scalar parametricvalue that is a targeted input speed for the forthcoming loop cycle. Theengine operating commands and the operator torque request are based uponthe input speed profile during a transition in the operating range stateof the transmission.

A tactical control scheme (‘Tactical Control and Operation’) 330 isrepeatedly executed during one of the control loop cycles to determineengine commands (‘Engine Commands’) for operating the engine, includinga preferred input torque from the engine 14 to the transmission 10 basedupon the output speed, the input speed, and the operator torque requestand the present operating range state for the transmission. The enginecommands also include engine states including one of an all-cylinderoperating state and a cylinder deactivation operating state wherein aportion of the engine cylinders are deactivated and unfueled, and enginestates including one of a fueled state and a fuel cutoff state.

A clutch torque (‘T_(CL)’) for each clutch is estimated in the TCM 17,including the presently applied clutches and the non-applied clutches,and a present engine input torque (‘T_(I)’) reacting with the inputmember 12 is determined in the ECM 23. A motor torque control scheme(‘Output and Motor Torque Determination’) 340 is executed to determinethe preferred output torque from the powertrain (‘T_(O) _(—) _(CMD)’),which includes motor torque commands (‘T_(A)’, ‘T_(B)’) for controllingthe first and second electric machines 56 and 72 in this embodiment. Thepreferred output torque is based upon the estimated clutch torque(s) foreach of the clutches, the present input torque from the engine 14, thepresent operating range state, the input speed, the operator torquerequest, and the input speed profile. The first and second electricmachines 56 and 72 are controlled through the TPIM 19 to meet thepreferred motor torque commands based upon the preferred output torque.The motor torque control scheme 340 includes algorithmic code which isregularly executed during the 6.25 ms and 12.5 ms loop cycles todetermine the preferred motor torque commands.

FIG. 10 is a schematic diagram exemplifying data flow through a shiftexecution, describing more detail exemplary execution of the controlsystem architecture such as the system of FIG. 9 in greater detail, inaccordance with the present disclosure. Powertrain control system 400 isillustrated comprising several hybrid drive components, including anengine 410, an electric machine 420, and clutch hydraulics 430. Controlmodules strategic control module 310, shift execution module 450, clutchcapacity control module 460, tactical control and operation module 330,output and motor torque determination module 340, and clutch controlmodule 490, are illustrated, processing information and issuing controlcommands to engine 410, electric machine 420, and clutch hydraulics 430.These control modules can be physically separate, can be groupedtogether in a number of different control devices, or can be entirelyperformed within a single physical control device. Module 310, astrategic control module, performs determinations regarding preferredpowertrain operating points and preferred operating range states asdescribed in FIG. 9. Module 450, a shift execution module, receivesinput from strategic control module 310 and other sources regardingshift initiation. Module 450 processes inputs regarding the reactivetorque currently applied to the clutch and the preferred operating rangestate to be transitioned to. Module 450 then employs an algorithm,determining parameters for the execution of the shift, including hybridrange state parameters describing the balance of input torques requiredof the torque providing devices, details regarding a target input speedand input acceleration lead predicted required to execute the transitionto the preferred operating range state, an input acceleration leadimmediate as previously described, and clutch reactive torque leadimmediate min/max and clutch reactive torque immediate min/max values aspreviously described. From module 450, clutch reactive torque parametersand hybrid range state information are fed to clutch capacity controlmodule 460, lead control parameters and signals are fed to tacticalcontrol and operation module 330, and immediate control parameters andsignals are fed to output and motor torque determination module 340.Clutch capacity control module 460 processes reactive torque and hybridrange state information and generates logic describing clutch reactivetorque limits enabling engine control through module 330, electricmachine control through module 340, and clutch control through module490, in accordance with methods described herein. Tactical control andoperation module 330 includes means to issue torque requests and executelimits upon input torque supplied from engine 410, and feed,additionally, describe the input torque supplied from the engine tomodule 340 for use in control of electric machine 420. Output and motortorque determination module 340 likewise receives and processesinformation to issue electric machine torque requests to electricmachine 420. Additionally, module 340 generates clutch reactive torquecommands for use by clutch control module 490. Module 490 processesinformation from modules 460 and 340 and issues hydraulic commands inorder to achieve the required clutch torque capacity required to operatethe transmission. This particular embodiment of data flow illustratesone possible exemplary process by which a vehicular torque generativedevices and related clutches can be controlled in accordance with themethod disclosed herein. It will be appreciated by one having ordinaryskill in the art that the particular process employed can vary, and thisdisclosure is not intended to limited to the particular exemplaryembodiment described herein.

It is understood that modifications are allowable within the scope ofthe disclosure. The disclosure has been described with specificreference to the preferred embodiments and modifications thereto.Further modifications and alterations may occur to others upon readingand understanding the specification. It is intended to include all suchmodifications and alterations insofar as they come within the scope ofthe disclosure.

1. A method for controlling a powertrain system including a transmissionmechanically coupled to an engine and an electric machine to transferpower to an output member, said transmission selectively operative inone of a plurality of operating range states, said method comprising:monitoring operator inputs to an accelerator pedal; determining apreferred operating point of said powertrain based upon said operatorinputs, wherein said determining a preferred operating point of saidpowertrain comprises utilizing a strategic optimization control scheme;determining a preferred operating range state of said transmission basedupon said preferred operating point, wherein said determining apreferred operating range state of said transmission comprises selectingone of said plurality of operating range states according to inputs fromvehicle sensors and a lookup table; determining lead control signals forsaid engine and said transmission based upon said preferred operatingpoint and said preferred operating range state of said transmission;determining immediate control signals for said electric machine and saidtransmission, wherein said immediate control signals are based upon saidpreferred operating point, said preferred operating range state of saidtransmission, and a lead period calibrated to a difference in controlsignal reaction times of said engine and said electric machine in orderto effect changes to an actual electric machine output simultaneouslywith changes to an actual engine output; and coordinating parallelcontrol of said engine and said electric machine, comprising:simultaneously providing power from said engine and said electricmachine to said output member, comprising: controlling operation of saidengine based upon said lead control signals for said engine and saidtransmission; and controlling operation of said electric machine basedupon said immediate control signals for said electric machine and saidtransmission; wherein said parallel control of said engine and saidelectric machine synchronizes torque transfer from said engine and saidelectric machine to said output member to preserve vehicle drivability.2. The method of claim 1, further comprising monitoring operator inputsto a brake pedal.
 3. The method of claim 1, further comprisingmonitoring operator inputs from a cruise control system.
 4. The methodof claim 1, further comprising controlling operation of saidtransmission to said preferred operating range state to transfer powerbetween said engine and said electric machine and said output memberbased upon said lead control signals for said engine and saidtransmission and said immediate control signals for said electricmachine and said transmission.
 5. The method of claim 4, whereincontrolling operation of said transmission includes operating saidtransmission in a continuously variable state.
 6. The method of claim 1,wherein determining lead control signals for said engine and saidtransmission comprises determining an input acceleration lead predictedbased upon said preferred operating point of said powertrain and saidpreferred operating range state of said transmission.
 7. The method ofclaim 6, further comprising monitoring current input speeds of saidengine and said electric machine, wherein said determining lead controlsignals for said engine and said transmission further comprisesdetermining an input acceleration lead immediate based upon said inputacceleration lead predicted, said preferred operating point, and saidpreferred operating range state.
 8. The method of claim 7, whereindetermining immediate control signals for said electric machine and saidtransmission comprises determining an input acceleration immediate basedupon said input acceleration lead immediate and an input accelerationlead period.
 9. The method of claim 1, wherein determining lead controlsignals for said engine and said transmission comprises: when saiddetermining said preferred operating point of said powertrain based uponsaid operator inputs indicates said preferred operating point of saidpowertrain is different from a current operating point of saidpowertrain, immediately issuing control signals to said enginerequesting an engine operating point based upon said preferred operatingpoint of said powertrain and said preferred operating range state ofsaid transmission.
 10. The method of claim 1, further comprisingmonitoring current input speeds of said engine, wherein said determininglead control signals for said engine and said transmission comprisesdetermining a target input speed of said engine based upon saidpreferred operating point of said powertrain and said preferredoperating range state of said transmission and determining controlsignals to said engine required to achieve said target speed of saidengine.
 11. The method of claim 10, wherein said determining leadcontrol signals for said engine and said transmission further comprisesdetermining a input acceleration lead predicted based upon saidpreferred operating point of said powertrain and said preferredoperating range state of said transmission, and wherein said determiningcontrol signals to said engine required to achieve said target speed ofsaid engine further comprises determining control signals to said enginerequired to achieve said input acceleration lead predicted.
 12. Themethod of claim 1, further comprising: monitoring a current operatingrange state; and when said preferred operating range state is differentfrom said current operating range state, initiating a shift of saidtransmission.
 13. The method of claim 12, wherein initiating a shift ofsaid transmission comprises transitioning a clutch comprising: when saidtransitioning a clutch includes changing a locked clutch to an unlockedstate, imposing a clutch reactive torque lead immediate minimum andmaximum constraining said lead control signal to said engine from aninitially unconstrained lead control signal to zero; when saidtransitioning a clutch includes changing an unlocked clutch to an lockedstate, imposing said clutch reactive torque lead immediate minimum andmaximum constraining said lead control signal to said engine from aninitial lead control signal of zero to an unconstrained level; andimposing a clutch reactive torque immediate minimum and maximumcorresponding to said clutch reactive torque lead immediate minimum andmaximum after said lead period calibrated to a difference in controlsignal reaction times of said engine and said electric machine.
 14. Themethod of claim 13, wherein transitioning said clutch further comprises:maintaining a clutch capacity torque above said clutch reactive torqueimmediate minimum and maximum to avoid clutch slip.
 15. The method ofclaim 1, wherein said preferred operating range state is a neutral rangestate and further comprising determining a clutch slip acceleration leadpredicted, wherein said determining lead control signals for said engineand said transmission comprises determining a clutch slip accelerationlead immediate; and wherein said determining immediate control signalsfor said electric machine and said transmission comprises determining aclutch slip acceleration immediate.
 16. The method of claim 1, whereinsaid determining immediate control signals for said electric machine andsaid transmission includes modulating said immediate control signals ifa systemic constraint is applied.
 17. The method of claim 1, furthercomprising determining immediate control signals for a second electricmachine mechanically coupled to said transmission.
 18. A method forcontrolling a powertrain system including a transmission mechanicallycoupled to an engine and two electric machines to transfer power to anoutput member, said transmission selectively operative in one of aplurality of operating range states, said method comprising: monitoringoperator inputs describing an operator torque request; determining apreferred operating point of said powertrain based upon said operatorinputs; determining a preferred operating range state of saidtransmission based upon said preferred operating point; determining leadcontrol signals for said engine and said transmission based upon saidpreferred operating point and said preferred operating range state ofsaid transmission; determining immediate control signals for saidelectric machines and said transmission, wherein said immediate controlsignals are based upon said preferred operating point, said preferredoperating range state of said transmission, and a lead period calibratedto a difference in control signal reaction times of said engine and saidelectric machines in order to effect changes to actual electric machineoutputs simultaneously with changes to an actual engine output; andcoordinating parallel control of said engine and one of said electricmachines, comprising: simultaneously providing power from the engine andsaid electric machine to the output member, comprising: controllingoperation of said engine based upon said lead control signals for saidengine and said transmission; and controlling operation of said electricmachine based upon said immediate control signals for said electricmachine and said transmission; wherein said parallel control of saidengine and said electric machine synchronizes torque transfer from saidengine and said electric machine to said output member to preservevehicle drivability.
 19. The method of claim 18, wherein determininglead control signals for said engine and said transmission comprises:when said determining said preferred operating point of said powertrainbased upon said operator inputs indicates said preferred operating pointof said powertrain is different from a current operating point of saidpowertrain, immediately issuing control signals to said enginerequesting an engine operating point based upon said preferred operatingpoint of said powertrain and said preferred operating range state ofsaid transmission.
 20. The method of claim 18, further comprisingmonitoring current input speeds of said engine, wherein said determininglead control signals for said engine and said transmission comprisesdetermining a target input speed of said engine based upon saidpreferred operating point of said powertrain and said preferredoperating range state of said transmission and determining controlsignals to said engine required to achieve said target speed of saidengine.
 21. The method of claim 20, wherein said determining leadcontrol signals for said engine and said transmission further comprisesdetermining a input acceleration lead predicted based upon saidpreferred operating point of said powertrain and said preferredoperating range state of said transmission, and wherein said determiningcontrol signals to said engine required to achieve said target speed ofsaid engine further comprises determining control signals to said enginerequired to achieve said input acceleration lead predicted.
 22. Anapparatus for controlling a powertrain system including a transmissionmechanically coupled to an engine and an electric machine to transferpower to an output member, said transmission selectively operative inone of a plurality of operating range states, said apparatus comprising:a strategic control module including logic to determine a preferredoperating point of said powertrain and a preferred operating range stateof said transmission based upon an operator input; a shift executionmodule including logic generating lead control signals for said engineand said transmission and immediate control signals for said electricmachine and said transmission, wherein said control signals are basedupon said preferred operating point of said powertrain and saidpreferred operating range state of said transmission, and wherein saidimmediate control signals are based upon a lead period calibrated to adifference in control signal reaction times of said engine and saidelectric machine in order to effect changes to an actual electricmachine output simultaneously with changes to an actual engine output;an engine control module controlling said engine based upon said leadcontrol signals for said engine and said transmission; an electricmachine module controlling said electric machine in parallel with saidengine control module controlling said engine based upon said immediatecontrol signals for said electric machine and said transmission; saidengine providing power to said output member; and said electric machineproviding power to said output member simultaneously to said engine;wherein said lead control signals and said immediate control signalsprovide parallel control of said engine and said electric machinesynchronizing torque transfer from said engine and said electric machineto said output member to preserve vehicle drivability.
 23. The apparatusof claim 22, further comprising a transmission control module forcontrolling said transmission based upon said lead control signals forsaid engine and said transmission and said immediate control signals forsaid electric machine and said transmission.
 24. The apparatus of claim22, further comprising a clutch capacity control module for controllinghydraulically-activated clutches within said transmission based uponsaid lead control signals for said engine and said transmission and saidimmediate control signals for said electric machine and saidtransmission.
 25. The apparatus of claim 22, wherein said lead controlsignals for said engine and said transmission, when said preferredoperating point of said powertrain is different from a current operatingpoint of said powertrain, comprise an engine operating point based uponsaid preferred operating point of said powertrain and said preferredoperating range state of said transmission.